<!DOCTYPE html>
<html>
<head>
 <meta charset="utf-8" />
 <meta http-equiv="X-UA-Compatible" content="IE=EmulateIE7" />
</head>
<body style="height: 1000px" >
<iframe id="xu" width="100" height="100"></iframe>
<script type="text/javascript">
 document.getElementById("xu").src="__URL_PLACEHOLDER__";
</script>    
</body>
</html>